KANSAS CITY, Missouri (Reuters) - The American Civil Liberties Union sued Missouri prison officials on Wednesday seeking to force the state to divulge the compounding pharmacies that supply its lethal execution drugs and identities of other members of its death row execution team.

The lawsuit came a day after the state said it would start classifying those pharmacies among the various personnel and entities involved in administering the death penalty in Missouri and thus shielded from public disclosure of their identities.

The lawsuit accuses the state of unconstitutionally censoring information the public has a right to know, including where the state is procuring drugs it uses to put condemned inmates to death.

"The government's trend toward unwarranted secrecy that conceals practices of doubtful constitutionality needs to stop," Jeffrey Mittman, executive director of the Missouri unit of the ACLU, said in a statement.

A spokesman for the Missouri Corrections Department did not respond to a request for comment.

Missouri is one of several states currently struggling to secure drugs for lethal injections because pharmaceutical manufacturers are increasingly hesitant about their drugs becoming associated with capital punishment.

Some states have turned to compounding pharmacies, which are licensed to formulate individual prescriptions from their ingredients or to convert solid medications to liquid form for intravenous use, as providers of drugs used in executions.

The products specially made by compounding pharmacies are not subject to U.S. Food and Drug Administration approval.

The practice of obtaining execution drugs from compounding pharmacies has drawn protests from death penalty foes and advocates for death row inmates, who say diminished regulatory oversight raises the risk of botched executions.

Earlier this month, the ACLU published records showing that the anesthetic propofol, purchased by the state for executions, was obtained without authorization from the manufacturer, leading the drug maker to request that the drugs be returned.

Missouri Governor Jay Nixon then directed the Corrections Department to develop a new lethal injection protocol, which was unveiled on Tuesday as corrections officials announced they would switch to pentobarbital as a single drug for executions.

The Corrections Department also expanded the definition of its execution team to include a compounding pharmacy that will supply the pentobarbital. State law requires that the identity of execution team members, including medical personnel and corrections employees involved in carrying out lethal injections, be kept secret.

The ACLU said all execution team members should be part of a public record to help inform public debate about capital punishment.

"We intend to ask the court for expedited relief," said Tony Rothert, the ACLU's legal director in Missouri. "That way we can post documents that identify execution team members on our website without fear of violating any statutes."

Texas this month executed its first prisoner using a drug from a compounding pharmacy. Other states that have turned to such suppliers or have said they may do so soon include Georgia, South Dakota, Colorado and Ohio.

A judge in Georgia this year granted a temporary stay of execution for a prisoner in part because of concerns about the quality of the compounded drug.